Diclofenac topical formulation

ABSTRACT

The present invention provides a gel formulation comprising diclofenac sodium which has superior transdermal flux properties, which may be used for the topical treatment of pain, such as in osteoarthritis.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/497,096, filed Sep. 25, 2014 which is a continuation of U.S.application Ser. No. 14/025,781, filed Sep. 12, 2013, which applicationis a continuation of U.S. application Ser. No. 13/564,688, filed Aug. 1,2012, now U.S. Pat. No. 8,563,613, which application is a continuationof U.S. application Ser. No. 12/134,121, filed Jun. 5, 2008, now U.S.Pat. No. 8,252,838, which application is a continuation ofPCT/US2007/081674, filed Oct. 17, 2007, which application claimspriority to U.S. Provisional Application No. 60/829,756, filed Oct. 17,2006, the teachings all of which are incorporated herein by reference intheir entireties for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to compositions and methods fortreating osteoarthritis.

BACKGROUND OF THE INVENTION

1. Osteoarthritis

Osteoarthritis (OA) is a chronic joint disease characterized byprogressive degeneration of articular cartilage. Symptoms include jointpain and impaired movement. OA is one of the leading causes ofdisability worldwide and a major financial burden to health caresystems. It is estimated to affect over 15 million adults in the UnitedStates alone. See Boh L. E. Osteoarthritis. In: DiPiro J. T., Talbert R.L., Yee G. C., et al., editors. Pharmacotherapy: a pathophysiologicalapproach. 4th ed. Norwalk (Conn.): Appleton & Lange, pp. 1441-59 (1999).

Oral non-steroidal anti-inflammatory drugs (NSAIDs) are a mainstay inthe management of OA. They have analgesic, anti-inflammatory andantipyretic effects and are useful in reducing pain and inflammation.NSAIDS are however associated with serious potential side effectsincluding nausea, vomiting, peptic ulcer disease, GI haemorrhage, andcardiovascular events.

Topical NSAIDs offer the possibility of achieving local therapeuticbenefit while reducing or eliminating the risk of systemic side effects.There has been widespread interest in this approach to treating OA, butdata in support of the efficacy of topical NSAIDs in the treatment of OAis limited. For instance, a study of 13 randomized placebo controlledtrials (RCT's) of various topical NSAIDs tested specifically for use inthe treatment of OA concluded that they were not generally efficaciousfor chronic use in OA. (Lin et al., Efficacy of topical non-steroidalanti-inflammatory drugs in the treatment of osteoarthritis:meta-analysis of randomized controlled trials, BMJ,doi:10.1136/bmj.38159.639028.7C (2004)).

There are generally three outcomes used to measure the efficacy of an OAtreatment: pain, physical function, and a patient global assessment. SeeBellamy N., Kirwan J., Boers M., Brooks P., Strand V., Tugwell P., etal. Recommendations for a core set of outcome measures for future phaseIII clinical trials in knee, hip and hand osteoarthritis. Consensusdevelopment at OMERACT III., J Rheumatol, 24:799-802 (1997). To besuitable for chronic use, a therapy must generally show efficacy onthese three variables over a sustained period of time. In the U.S. forinstance, the Food and Drug Administration (FDA) requires OA therapiesto show superiority over placebo over a 12 week period. Notwithstandingthe significant potential for topical NSAIDs in the treatment of OA, asof the time of filing this application, none have been approved for suchtreatment in the U.S.

U.S. Pat. Nos. 4,575,515 and 4,652,557 disclose topical NSAIDcompositions, one of which, consisting of 1.5% diclofenac sodium, 45.5%dimethylsulphoxide, 11.79% ethanol, 11.2% propylene glycol, 11.2%glycerine, and water, has been shown to be effective in chronic OAtreatment. See Towheed, Journal of Rheumatology 33:3 567-573 (2006) andalso Oregon Evidence Based Practice Center entitled “Comparative Safetyand Effectiveness of Analgesics for Osteoarthritis”, AHRQ Pub. No.06-EHC009-EF. This particular composition is referred to herein as“comparative liquid formulation” or “comparative” in the Examplessection. However, the compositions of these prior inventions havedrawbacks in that they are slow to dry and runny. They also requirefrequent dosing of three to four times a day to achieve efficacy in OA,which increases exposure to potential skin irritants and increases therisk of skin irritation.

In general, the failure of topical NSAIDs to fulfill their promise in OAmay be due in part to the difficulty associated with delivering amolecule through the skin in sufficient quantities to exert atherapeutic effect and in a manner that makes the treatment itselftolerable. It is generally believed that clinical efficacy in OArequires absorption of the active ingredient and its penetration insufficient quantities into underlying inflamed tissues including thesynovium and synovial fluid of joints. See Rosenstein, Topical agents inthe treatment of rheumatic disorders, Rheum. Dis. Clin North Am., 25:899-918 (1999).

However, the skin is a significant barrier to drug permeation, anddespite nearly four decades of extensive research, the success oftransdermal drug delivery in general remains fairly limited with only asmall number of transdermal drug products commercially available.

In connection with topical dosage forms applied to the skin, a number ofinteractions can occur including vehicle-skin, vehicle-drug, anddrug-skin. Each can affect the release of an active agent from a topicaldosage form (Roberts, M. S.: Structure-permeability considerations inpercutaneous absorption. In Prediction of Percutaneous Penetration, ed.by R. C. Scott et al., vol. 2, pp. 210-228, IBC Technical Services,London, 1991). Thus various factors can affect absorption rates andpenetration depth including the active ingredient, the vehicle, the pH,and the relative solubility of the active in the vehicle versus the skin(Ostrenga J. et al., Significance of vehicle composition I: relationshipbetween topical vehicle composition, skin penetrability, and clinicalefficacy, Journal of Pharmaceutical Sciences, 60: 1175-1179 (1971)).More specifically, drug attributes such as solubility, size and charge,as well as, vehicle attributes such as the drug dissolution rate,spreading-ability, adhesion, and ability to alter membrane permeabilitycan have significant effects on permeability.

There is significant variability observed from seemingly minorvariations in formulations. For instance, Naito demonstrates significantvariability in penetration among topical NSAID formulations simply bychanging the gelling agent used in the compositions (Naito et al.,Percutaneous absorption of diclofenac sodium ointment, Int. Jour. ofPharmaceutics, 24: 115-124 (1985)). Similarly, Ho noted significantvariability in penetration by changing the proportions of alcohol,propylene glycol, and water (Ho et al., The influence of cosolvents onthe in-vitro percutaneous penetration of diclofenac sodium from a gelsystem, J Pharm. Pharmacol., 46:636-642 (1994)). It was noted that thechanges affected three distinct variables: (i) the solubility of thedrug in the vehicle, (ii) the partition coefficient, and (iii) effectson alteration of skin structure.

Ho et al. (1994) also noted that (i) the pH of the vehicle, (ii) thedrug solubility, and (iii) the viscosity of a gel matrix can influencepenetration from a gel dosage form. The pH value affects the balancebetween ionized and non-ionized forms of the drug, which have differentpenetration properties (Obata, International Journal of Pharmaceutics,89: 191-198 (1993)). The viscosity can affect diffusion of the drugthrough the gel matrix and release of the drug from the vehicle into theskin. The solubility of the drug in the vehicle will affect thepartition coefficient of the drug between the formulation and therecipient membrane/tissue (Ho et al. 1994).

Chemical penetration enhancers are one means for reversibly lowering theskin barrier. Other methods include iontophoresis, ultrasound,electroporation, heat, and microneedles. At least 250 chemicals havebeen identified as enhancers that can increase skin permeability.General categories include pyrrolidones, fatty acids, esters andalcohols, sulfoxides, essential oils, terpenes, oxazoldines,surfactants, polyols, azone and derivatives, and epidermal enzymes.

The mechanisms by which penetration enhancers reduce the skin barrierfunction are not well understood (see Williams and Barry “PenetrationEnhancers” Advanced Drug Delivery Reviews 56: 603-618 (2004)) althoughit has been proposed that the mechanisms can be grouped into three broadcategories: lipid disruption, increasing corneocyte permeability, andpromoting partitioning of the drug into the tissue.

The challenge with use of chemical penetration enhancers is that fewseem to induce a significant or therapeutic enhancement of drugtransport at tolerable levels. This is because the act of disrupting theskin barrier will have the potential of causing skin irritation. Withincreased disruption, skin irritation will become a greater issue. Thisis particularly problematic with topical OA treatments where the goal isto have the active penetrate into joint tissue and where the drug mustbe utilized on a long-term basis due to the nature of the disease. Theinventors have developed methods and compositions that deliver moreactive ingredient per unit dose than previously known compositions, andthis would be expected to lead to a lower incidence of skin irritation.

The compositions of the invention use diclofenac sodium which is acommonly used NSAID. Diclofenac has four different salts that showsignificant variability in the degree of permeation in solutions usingdifferent solvents. Minghetti, for instance, teaches that a diclofenacsalt with an organic base is best for topical applications (Minghetti etal., Ex vivo study of trandermal permeation of four diclofenac saltsfrom different vehicles, Jour. of Pharm. Sci, DOI 10.1002/jps.20770(2007)).

Other research points to microemulsion formulations as a means fordelivery of diclofenac sodium (Kantarci et al., In vitro permeation ofdiclofenac sodium from novel microemulsion formulations through rabbitskin, Drug Development Research, 65:17-25 (2005); and Sarigullu I. etal., Transdermal delivery of diclofenac sodium through rat skin fromvarious formulations, APS PharmSciTech, 7(4) Article 88, E1-E7 (2006)).

Other topical diclofenac compositions are disclosed in a number ofpatents including U.S. Pat. No. 4,543,251, U.S. Pat. No. 4,670,254, U.S.Pat. No. 5,374,661, U.S. Pat. No. 5,738,869, U.S. Pat. No. 6,399,093 andU.S. Pat. No. 6,004,566. U.S. Patent Application No. 20050158348 pointsout that various solvents are widely used for gel preparations, butnotes that they are limited in potential due to skin irritation. Thisreference also notes that gel compositions are associated with fasttermination of action as the active precipitates from solution in theupper skin layers, limiting anti-inflammatory action in deeper tissues.The gels of the present invention are designed to accomplish theopposite, namely prolonged action and anti-inflammatory action in thedeeper tissues.

2. Gel Formulations of Diclofenac

None of the previous references disclose the compositions of theinvention or their use in the treatment of OA. Rather, these referenceshighlight the significant unmet need with respect to topical OAtreatments for chronic use and the complexity of transdermal transportin general, where significant variability in permeation is observed bychanging composition elements or their relative proportions.

In light of the foregoing, there is a considerable need for improvementin the development of a topical NSAID suitable for long term use in thetreatment of OA. The challenge has been to develop an optimalformulation which will deliver the active agent to the underlying tissuein sufficient concentration to treat OA on a long term basis, whilereducing or minimizing the incidence of intolerable skin irritationcaused by disrupting the skin barrier and while providing a formulationand dosage that leads to and encourages patient compliance. The presentinvention satisfies these and other needs.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art byproviding diclofenac sodium gel formulations for the treatment ofosteoarthritis that display a better drying time, higher viscosity,increased transdermal flux, and greater pharmacokinetic absorption invivo when compared to previously described compositions. Furthermore,the preferred diclofenac sodium gel formulations of the presentinvention provide other advantages including favorable stability at six(6) months as reflected in the lack of any substantial changes inviscosity, the absence of phase separation and crystallization at lowtemperatures, and a low level of impurities. Moreover, the present gelformulations adhere well to the skin, spread easily, dry quicker, andshow greater in vivo absorption in comparison to previously describedcompositions. Thus, the gel formulations of the present inventionprovide superior means for delivery of diclofenac sodium through theskin for the treatment of osteoarthritis, as compared to previouslydescribed formulations.

As such, in one embodiment, the present invention provides a gelformulation comprising, consisting essentially of, or consisting of:

-   -   (i) diclofenac sodium;    -   (ii) DMSO;    -   (ii) ethanol;    -   (iii) propylene glycol;    -   (v) a thickening agent;    -   (vi) optionally glycerol; and    -   (vii) water.

In another embodiment, the present invention provides a method oftreating osteoarthritis in a subject suffering from articular pain, themethod comprising the topical administration to an afflicted joint areaof a subject a therapeutically effective amount of a gel formulationcomprising, consisting essentially of, or consisting of:

-   -   (i) diclofenac sodium;    -   (ii) DMSO;    -   (ii) ethanol;    -   (iii) propylene glycol;    -   (v) a thickening agent;    -   (vi) optionally glycerol; and    -   (vi) water,        thereby treating osteoarthritis.

A further embodiment provides for the use of diclofenac sodium in thepreparation of a medicament for the treatment of pain, the medicamentcomprising a gel formulation comprising, consisting essentially of, orconsisting of:

-   -   (i) diclofenac sodium;    -   (ii) DMSO;    -   (ii) ethanol;    -   (iii) propylene glycol;    -   (v) a thickening agent;    -   (vi) optionally glycerol; and    -   (vii) water.

In yet a further embodiment, the present invention provides a gelformulation comprising, consisting essentially of, or consisting of: adiclofenac sodium solution and at least one thickening agent, which canbe selected from cellulose polymer, a carbomer polymer, a carbomerderivative, a cellulose derivative, polyvinyl alcohol, poloxamers,polysaccharides, and mixtures thereof.

In an aspect of this embodiment, the diclofenac sodium solutioncomprises, consists essentially of, or consists of:

-   -   (i) diclofenac sodium;    -   (ii) DMSO;    -   (ii) ethanol;    -   (iii) propylene glycol;    -   (iv) optionally glycerol; and    -   (v) water.

In an aspect of the above embodiments, the thickening agents can beselected from cellulose polymers, carbomer polymers, a carbomerderivative, a cellulose derivative, polyvinyl alcohol, poloxamers,polysaccharides, and mixtures thereof.

In an aspect of the above gel embodiments, diclofenac sodium is presentat 1-5% w/w, such as 1, 2, 3, 4, or 5% w/w; DMSO is present at 30-60%w/w; ethanol is present at 1-50% w/w; propylene glycol is present at1-15% w/w; glycerol is present at 0-15% w/w, a thickening agent ispresent such that the end viscosity of the gel is between 10 and 50000centipoise; and water is added to make 100% w/w. In other aspects,glycerol is present at 0-4% w/w. In further aspects, no glycerol ispresent.

In another aspect of the above embodiments, diclofenac sodium is presentat 2% w/w; DMSO is present at 45.5% w/w; ethanol is present at 23-29%w/w; propylene glycol is present at 10-12% w/w; hydroxypropylcellulose(HY119) is present at 0-6% w/w; glycerol is present at 0-4%, and wateris added to make 100% w/w. In other aspects, there is no glycerol in thegel formulation. In further aspects, the end viscosity of the gel is500-5000 centipoise.

A feature of the above gel formulations is that when such formulationsare applied to the skin, the drying rate is quicker and transdermal fluxis higher than previously described compositions, such as those in U.S.Pat. Nos. 4,575,515 and 4,652,557. Additional features of the preferredformulations include decreased degradation of diclofenac sodium, whichdegrades by less than 0.04% over the course of 6 months and a pH of6.0-10.0, for example around pH 9.0.

In certain embodiments, the gel formulations of the invention comprise1-5% glycerol, wherein the gel formulation when applied to the skin hasa drying rate and transdermal flux greater than a comparative liquidformulation. In some aspects, the drying rate results in a residue of atmost 50% of a starting amount after 24 hours and the transdermal flux is1.5 or more greater than a comparative liquid formulation as determinedby Franz cell procedure at finite or infinite dosing or both.

In other embodiments, the gel formulations and methods of their useprovide a reduction of pain over 12 weeks when the formulations areapplied topically. In various aspects, the gel formulations are appliedtwice daily and the pain can be due to osteoarthritis.

These and other objects, embodiments, and advantages will become moreapparent when read with the figures and detailed description whichfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a bar graph of flux rate of HEC and PVP gels. Franzdiffusion cells were dosed at 15 mg per Franz cell.

FIG. 2 shows a bar graph of flux rate of gels made with Carbopol 981 andUltrez 10. Franz diffusion gels were dosed with 200 μl per Franz cell.

FIG. 3 shows a bar graph of flux rate of carbopol 971 and carbopol 981gels. Franz diffusion cells were dosed at 50 μl per cell.

FIG. 4 shows a bar graph of flux rate of various gels and a comparativeliquid formulation. Franz cells were dosed at 10 mg per Franz cell.

FIG. 5 shows a bar graph illustrating the effect of the pH of variousgels and a comparative liquid formulation on flux rate. Franz diffusioncells were dosed at 7 mg per cell.

FIG. 6 shows a bar graph of flux rates of various gels. Franz cells weredosed at 7 mg per Franz cell.

FIG. 7 shows a bar graph of flux rates of various diclofenacformulations. The comparative liquid formulation (1.5% diclofenacsodium) was dosed at 20 mg per Franz cell, Solaraze® (a commerciallyavailable 3% diclofenac sodium gel) was dosed at 10 mg per Franz cell,and a formulation of the invention, F14/2, was dosed at 15 mg per Franzdiffusion cell. At this dosing, all cells were dosed with equivalentamounts of diclofenac sodium.

FIG. 8 shows a bar graph of flux rates in multidosing experiments. Thecomparative liquid formulation was dosed at 0.9 mg per Franz cell at 0,4, 8, and 12 hrs. A formulation of the invention, F14/2, was dosed at1.5 mg per Franz cell at 0 and 6 hrs.

FIG. 9 shows a bar graph of flux rates of various diclofenacformulations. Franz cells were dosed at 20 mg per cell.

FIG. 10 shows a bar graph of data on diclofenac flux rates from gelsdisclosed in Baboota et al. and gels of this invention. Franz cells weredosed at 4 mg per cell.

FIG. 11 shows the drying profile over time of three gel formulations andone liquid formulation of diclofenac sodium.

FIG. 12 shows the in vivo steady state plasma concentrations ofdiclofenac sodium after administration of either a liquid or gelformulation.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

The term “transdermal” is used herein to generally include a processthat occurs through the skin. The terms “transdermal” and “percutaneous”are used interchangeably throughout this specification.

The term “topical formulation” is used herein to generally include aformulation that can be applied to skin or a mucosa. Topicalformulations may, for example, be used to confer therapeutic benefit toa patient or cosmetic benefits to a consumer. Topical formulations canbe used for both topical and transdermal administration of substances.

The term “topical administration” is used herein to generally includethe delivery of a substance, such as a therapeutically active agent, tothe skin or a localized region of the body.

The term “transdermal administration” is used herein to generallyinclude administration through the skin. Transdermal administration isoften applied where systemic delivery of an active is desired, althoughit may also be useful for delivering an active to tissues underlying theskin with minimal systemic absorption.

The term “penetration enhancer” is used herein to generally include anagent that improves the transport of molecules such as an active agent(e.g., a medicine) into or through the skin. Various conditions mayoccur at different sites in the body either in the skin or below theskin creating a need to target delivery of compounds. For example, in atreatment for osteoarthritis, the delivery of the active agent intorelatively deep underlying joint tissue may be necessary to achievetherapeutic benefit. Thus, a “penetration enhancer” may be used toassist in the delivery of an active agent directly to the skin orunderlying tissue or indirectly to the site of the disease throughsystemic distribution. A penetration enhancer may be a pure substance ormay comprise a mixture of different chemical entities.

The term “finite dosing” is used herein to generally include anapplication of a limited reservoir of an active agent. The reservoir ofthe active agent is depleted with time leading to a tapering off of theactive absorption rate after a maximum absorption rate is reached.

The term “infinite dosing” is used herein to generally include anapplication of a large reservoir of an active agent. The reservoir isnot significantly depleted with time, thereby providing a long term,continuous steady state of active absorption.

As used herein, the term “comparative liquid formation” or “comparative”refers to a formulation such as that described in U.S. Pat. Nos.4,575,515 and 4,652,557 consisting of 1.5% diclofenac sodium, 45.5%dimethylsulfoxide, 11.79% ethanol, 11.2% propylene glycol, 11.2%glycerine, and water.

II. Gel Formulations

1. Components of the Gel Formulations

In order to provide a diclofenac sodium gel formulation having improvedproperties of drying time, increased transdermal flux and greaterpharmacokinetic absorption in vivo, higher viscosity, good adherence tothe skin, and ready spreadability, while maintaining stability overtime, the inventors have discovered that a surprisingly advantageouscombination of the following components can be used in the preparationof the gel compositions of the present invention.

The present invention provides gel formulations comprising an activeagent, preferably a non-steroidal anti-inflammatory drug orpharmaceutically acceptable salts thereof. More preferably, thenon-steroidal anti-inflammatory is diclofenac, which can exist in avariety of salt forms, including sodium, potassium, and diethylamineforms. In a preferred embodiment, the sodium salt of diclofenac is used.Diclofenac sodium may be present in a range of approximately 0.1% to10%, such as 1, 2, 3, 4, or 5% w/w. Use of the sodium salt has beenknown to create a challenge with respect to stability of an aqueous gelin that higher salt concentrations can cause a breakdown in the gelmatrix through interaction with certain thickening agents.

In another embodiment, the present invention includes a penetrationenhancer. The penetration enhancer may be dimethyl sulfoxide (“DMSO”) orderivatives thereof. The DMSO may be present in an amount by weight of1% to 70%, and more preferably, between 25% and 60%, such as 25, 30, 40,45, 50, 55, or 60% w/w. Preferably, DMSO is used in the presentinvention at a concentration of about 40 to about 50% w/w, such as 41,42, 43, 44, 45, 46, 47, 48, 49 and 50% and all fractions in between suchas 44, 44.5, 45, 45.5, 46, 46.5%, and the like.

In certain embodiments, the present invention includes a lower alkanol,such as methanol, ethanol, propanol, butanol or mixtures thereof. Incertain embodiments, the alkanol is present at about 1 to about 50% w/w.Preferably, ethanol is used at about 1-50% w/w, such as 1, 5, 10, 15,20, 25, 30, 35, 40, 45, or 50% w/w, and all fractions in between.

In certain embodiments, the present invention includes a polyhydricalcohol, such as a glycol. Suitable glycols include ethylene glycol,propylene glycol, butylene glycol, dipropylene glycol, hexanetriol and acombination thereof. Preferably, propylene glycol is used at about at1-15% w/w, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15%w/w, and all fractions in between.

In certain embodiments, the present invention includes glycerol (alsoreferred to herein as glycerine) at a concentration of 0-12% w/w.Preferably, glycerol is used at 0-4% w/w, such as 0, 1, 2, 3, or 4% w/w,and all fractions in between. In some embodiments, no glycerol is usedin the formulation.

In a preferred embodiment, the present invention provides a formulationcomprising a diclofenac solution and at least one thickening agent tomake a gel. The at least one thickening agent of the present inventionmay be an acrylic polymer (for example, Carbopol polymers, Noveonpolycarbophils and Pemulen polymeric emulsifiers available commerciallyfrom Noveon Inc. of Cleveland, Ohio), an acrylic polymer derivative, acellulose polymer, a cellulose polymer derivative, polyvinyl alcohol,poloxamers, polysaccharides or mixtures thereof. Preferably the at leastone thickening agent is hydroxypropylcellulose (HPC) used such that theend viscosity is between 10 and 50000 centipoise (cps). More preferablythe end viscosity is between 500 and 20000 cps.

The present gel formulation may optionally include at least oneantioxidant and/or one chelating agent.

Preferred antioxidants for use in the present invention may be selectedfrom the group consisting of butylated hydroxytoluene (BHT), butylatedhydroxyanisole (BHA), ascorbyl linoleate, ascorbyl dipalmitate, ascorbyltocopherol maleate, calcium ascorbate, carotenoids, kojic acid,thioglycolic acid, tocopherol, tocopherol acetate, tocophereth-5,tocophereth-12, tocophereth-18, tocophereth-80, and mixtures thereof.

Preferred chelating agents may be selected from the group consisting ofethylenediamine tetraacetic acid (EDTA), diammonium EDTA, dipotassiumEDTA, calcium disodium EDTA, HEDTA, TEA-EDTA, tetrasodium EDTA,tripotassium EDTA, trisodium phosphate, diammonium citrate, galactaricacid, galacturonic acid, gluconic acid, glucuronic acid, humic acid,cyclodextrin, potassium citrate, potassium EDTMP, sodium citrate, sodiumEDTMP, and mixtures thereof.

In addition, the topical formulations of the present invention can alsocomprise a pH adjusting agent. In one particular embodiment, the pHadjusting agent is a base. Suitable pH adjusting bases includebicarbonates, carbonates, and hydroxides such as alkali or alkalineearth metal hydroxide as well as transition metal hydroxides.Alternatively, the pH adjusting agent can also be an acid, an acid salt,or mixtures thereof. Further, the pH adjusting agent can also be abuffer. Suitable buffers include citrate/citric acid buffers,acetate/acetic acid buffers, phosphate/phosphoric acid buffers,formate/formic acid buffers, propionate/propionic acid buffers,lactate/lactic acid buffers, carbonate/carbonic acid buffers,ammonium/ammonia buffers, and the like. The pH adjusting agent ispresent in an amount sufficient to adjust the pH of the composition tobetween about pH 4.0 to about 10.0, more preferably about pH 7.0 toabout 9.5. In certain embodiments, the unadjusted pH of the admixedcomponents is between 8 and 10, such as 9, without the need for theaddition of any pH adjusting agents.

2. Characteristics of the Gel Formulation

a) Transdermal Flux

As shown below in the Examples, the present invention providesdiclofenac sodium gel formulations that display surprisingly effectiverates of transdermal flux when compared to previously describedformulations.

Accordingly, in one embodiment, the present gel formulation comprises anon-steroidal anti-inflammatory and at least one thickening agent andhaving a flux, as determined by a finite dose Franz cell procedure,equal to or greater than the flux of a comparative liquid formulation.Preferably, the flux is greater than the flux of the comparative liquidformulation. More preferably, the flux is at least 1.5 times greaterthan the flux of the comparative liquid formulation. In other words, theratio of: (i) the flux of the gel formulation comprising thenon-steroidal anti-inflammatory and at least one thickening agent to(ii) the flux of the comparative liquid formulation is preferablygreater than 1.0, and more preferably at least about 1.5.

In a further embodiment, the present invention further provides adiclofenac sodium gel formulation comprising a diclofenac solution andat least one thickening agent and having a flux as determined by thefinite Franz cell procedure at least equivalent to the flux of thediclofenac solution alone. Preferably, the diclofenac sodium gelformulation has a flux that is at least 2.0 times greater compared tothe flux of the diclofenac sodium solution alone. More preferably, thepresent invention provides a diclofenac sodium gel formulation having aflux that is at least 4.0 times greater compared to the flux of thediclofenac sodium solution alone. In other words, the ratio of: (i) theflux of the diclofenac sodium gel formulation to (ii) the flux of thediclofenac sodium solution is at least about 1.0, preferably at leastabout 2.0, more preferably at least about 4.0.

In a yet further embodiment, the present invention provides a diclofenacsodium gel formulation comprising diclofenac sodium and at least onethickening agent and having a flux as determined by the multiple finitedosing Franz cell procedure (dosing at 2.5 mg/cm² at 0 and 6 hours) ofat least 0.1 μg/hr/cm² at 24 hours, preferably at least 0.2 μg/hr/cm² at24 hours.

b) Viscosity

In another embodiment, the present invention provides a gel formulationcomprising a non-steroidal anti-inflammatory drug (NSAID) and at leastone thickening agent, the gel formulation having a viscosity of at least100 cP. Preferably, the gel formulation has a viscosity of at least 500cP. More preferably, the gel formulation has a viscosity of at least1000 cP. In other embodiments, the viscosity is 5000-10,000,10,000-15,000, or 15,000-20,000 cP.

In a further embodiment, the present invention provides a diclofenac gelformulation comprising a diclofenac solution and at least one thickeningagent, the gel formulation having a viscosity of around 1000 cP and aflux of at least 0.2 μg/cm²/hr as determined by the multiple finite doseFranz cell procedure (2.5 mg/cm² at 0 and 6 hours) at 24 hours.

c) Stability

The stability of a drug product composition can have a significantimpact on the length and cost of drug development, the nature of thestudies required to support regulatory submissions, and the ultimatesafety and approvability.

It is important for instance to minimize the amount of impurities ordegradation products that form over time due to interactions between thevarious ingredients in a composition. This can be particularly importantin compositions that are designed to increase skin permeability.

Thus, in some embodiments, the present invention provides a diclofenacsodium gel formulation that degrades by less than 1% over the course of6 months at room temperature. More preferably, the rate of degradationis less than 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or less than 0.1%,and all fractions in between, over the course of 6 months at roomtemperature.

d) Drying Time

Relative to previously disclosed compositions, such as those in U.S.Pat. Nos. 4,575,515 and 4,652,557 (termed herein as “comparative liquidformulation” or “comparative”), the compositions of the invention dryquicker while achieving higher transdermal flux of the drug. It issurprising that higher flux rate and quicker drying can be achievedtogether as skin hydration is known to increase transdermal flux orpenetration. The drying of the skin caused by rapid evaporation wouldtend to reduce the transdermal transport of drug remaining on the skin.The drying time difference is evident when equal amounts of the twoproducts are tested on opposite limbs. Within thirty (30) minutes thecompositions of the invention are almost completely dry whereas asignificant amount of the previously described liquid formulationremains.

To compare the drying times more quantitatively, side-by-sidecomparisons were conducted. To accomplish this, the inventors measuredthe residual weight of formulations by placing equal amounts (100 mg) ofa prior art formulation and compositions of the invention in weighingdishes over 10 cm² areas and weighing the amount remaining over time.Using this methodology, a difference is immediately noticeable, andbecomes dramatically different by 4 hours (Table 11 and FIG. 10).

e) Pharmacokinetics

A comparison of the absorption of diclofenac sodium of compositions ofthe invention and a comparable composition from U.S. Pat. Nos. 4,575,515and 4,652,557 was conducted in animals. The gels of the invention wereshown to have improved absorption on a per dose basis than thecomparative liquid compositions of these patents. In absolute terms, theclinical dose of the gels of the invention delivered a maximum observedplasma concentration (C_(max)) at steady state of 81 ng/ml and an areaunder the curve (AUC) of 584 ng/ml. This compared to 12 ng/ml and 106ng/ml for the comparator compositions.

These results speak to the properties of the vehicle in delivering theactive agent. The higher numbers for gel were seen even though thesolution composition was dosed four (4) times per day (total 5.2 ml)compared to twice (2) per day (total 4.0 ml) for the gels.

III Preparation of Gel Formulations

In another embodiment, the present invention provides a method formaking gel formulations of diclofenac sodium. The gel formulations ofthe present invention are preferably made by carrying out the followingsteps: (i) dispersing the thickener, derivative thereof and/or mixturethereof in dimethyl sulfoxide and stirring for 1 hour; (ii) dissolvingdiclofenac sodium in an aqueous alcohol mixture (e.g., an ethanol/watermixture); (iii) dispersing propylene glycol and glycerol into the NSAIDsolution from (ii); and (iv) mixing the resulting NSAID solution intothe thickener/dimethyl sulfoxide blend and stirring for 1 hour atambient temperature. Alternatively, the gel formulations of the presentinvention may be made by carrying out the following steps: (i)dissolving the NSAID (e.g., diclofenac sodium) in an alcohol solution ofDMSO (e.g., an ethanol/dimethyl sulfoxide mixture); (ii) dispersing thethickener, derivative thereof and/or mixture thereof in a solution ofwater/propylene glycol/glycerol and stirring for 1 hour; (iii) mixingthe NSAID solution from (i) into the thickener blend from (ii) andstirring for 1 hour at ambient temperature. Heating can also be usedduring these mixing processes to help facilitate the gel formation.

Diclofenac sodium may be present in a range of approximately 0.1% to 10%w/w, such as 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 7.0, 8.0,and 9.0% w/w.

IV Methods of Use

Compositions of the invention are particularly suited for use intreating osteoarthritis (OA) chronically. They may also be useful forthe treatment of other chronic joint diseases characterized by jointpain, degeneration of articular cartilage, impaired movement, andstiffness. Suitable joints include the knee, elbow, hand, wrist and hip.

Due to the properties of higher flux and greater in vivo absorption, itis believed that the formulations of the present invention can beadministered at lower dosing than previously described formulations. Inparticular, it is expected that the compositions of the invention can beused at twice a day dosing or once a day dosing in the treatment of OA.This would represent a significant improvement as lower dosing isassociated with better patient compliance, an important factor intreating chronic conditions.

Suitable amounts per administration will generally depend on the size ofthe joint, which varies per individual and per joint, however a suitableamount may range from 0.5 μl/cm² to 4.0 μl/cm². Preferably the amountranges from 2.0 to 3.0 μl/cm².

Compositions of the present invention may, if desired, be presented in abottle or jar or other container approved by the FDA, which may containone or more unit dosage forms containing the active ingredient. The packor dispenser may also be accompanied by a notice associated with thecontainer in a form prescribed by a governmental agency regulating themanufacture, use or sale of pharmaceuticals, which notice indicatesapproval by the agency of the form of the compositions for human orveterinary administration. Such notice, for example, may be of labelingapproved by the U.S. Food and Drug Administration for prescriptiondrugs, or of an approved product insert. Compositions comprising apreparation of the invention formulated in a compatible pharmaceuticalcarrier may also be prepared, placed in an appropriate container, andlabeled for treatment of an indicated condition.

The following examples are offered to illustrate, but not to limit, theclaimed invention.

V Examples Example 1 Materials and Methods

Table 1 provides a list of the materials used in the examples providedbelow:

TABLE 1 Materials Abbr Chemical FW Source Vendor # CAS BHA Butylatedhydroxyanisole 180.24 Sigma B1253 25013-16-5 BHT Butylatedhydroxytoluene 220.36 Spectrum BH110-07 128-37-0 Carb940 Carbopol 940Noveon Carbopol 940 9003-01-4 Carb971 Carbopol 971 Noveon Carbopol 9719003-01-4 Carb974 Carbopol 974 Noveon Carbopol 974 9003-01-4 Carb981Carbopol 981 Noveon Carbopol 981 9003-01-4 Carb1342 Carbopol 1342 NoveonCarbopol 1342 9003-01-4 Diclo Diclofenac Sodium 318.1 Labochim15307-79-6 DMSO Dimethyl Sulfoxide (USP) 78.1 Gaylord EM-2951 67-68-5EDTA Disodium Ethylenediaminetetraacetate VWR MK139504 6381-92-6Dihydrate EtOH Ethanol (USP) 46.1 Spectrum G1015 64-17-5 Gly Glycerin(USP) 92.1 Proctor & Gamble Superol V 56-81-5 Guar Guar gum SpectrumG1044 9000-30-0 HEC Hydroxyethyl cellulose - Natrasol 250 M HerculesNatrasol 250 M 9004-62-0 HPMC Hydroxypropyl methyl cellulose DowChemical Methocel E4M 9004-65-3 HY117 Hydroxpropyl cellulose 95,000Spectrum HY117 9004-64-2 HY119 Hydroxpropyl cellulose 370,000 SpectrumHY119 9004-64-2 Locu Locust Bean gum Spectrum L1135 9000-40-2 Peg300Poly(ethylene glycol) 300 (USP) ~300 Spectrum PO108 25322-68-3 PGPropylene Glycol (USP) 76.1 Dow Chemical 57-55-6 PVA Polyvinyl alcohol44.1 Sigma 81386 9002-89-5 PVP Polyvinyl pyrrolidone 360,000 Sigma 814409003-39-8 P407 Polxamer 407 Spectrum P1126 9003-11-6 Ultrez10 Ultrez 10Noveon Ultrez10 9003-01-4

The general methodology for preparation of each example provided is asfollows, unless otherwise indicated.

Final weight for each formulation was 25 g prepared in 50-mL glassvials. Vortexing or magnetic stir bars were used to mix the gels.

Viscosity was measured at 22° C. using Brookfield DV-III Ultra,programmable Rheometer with LV Spindle #31 at 10 rpm. For stabilitytesting, gels were stored at ambient temperature or in an incubator at50° C. Discoloration or changes in appearance including phase separationover time were evaluated.

The concentration of the DMSO was consistent in all of the experiments(45.5% w/w). Propylene glycol was at either 11 or 11.2% w/w. Ethanolconcentration varied from 11% to 30% w/w. Glycerol concentrations werevaried from 0 to 11.2% w/w. The diclofenac sodium concentration was ateither 1.5% (w/w) or 2% (w/w). Water was adjusted to compensate for theamount of inactives, thickening agents, and diclofenac sodium present insolution.

Franz diffusion cell experiments were used to analyze diclofenac sodiumflux rates of varying gel formulations across a substrate membrane.Franz diffusion cells are a common and well known method for measuringtransdermal flux rates. The general Franz cell procedure is described inFranz, T. J., Percutaneous absorption: on the relevance of in vitrodata. J Invest Derm, 64:190-195 (1975). The following was themethodology used in the present Examples.

Franz cells with a 3 ml receptor well volume were used in conjunctionwith split thickness cadaver skin (0.015″-0.018″, AlloSource). The donorwell had an area of ˜0.5 cm². Receptor wells were filled with isotonicphosphate buffered saline (PBS) doped with 0.01% sodium azide. Theflanges of the Franz cells were coated with vacuum grease to ensure acomplete seal and were clamped together with uniform pressure using apinch clamp (SS #18 VWR 80073-350). After Franz cells were assembled,the skin was allowed to pre-hydrate for 45 minutes with PBS. PBS wasthen removed and an appropriate amount of formulation is added to theskin. Dosing levels varied from 2 mg/cm² (considered finite dose) to 200mg/cm² (considered infinite dose). The donor well was then capped toprevent evaporation. Receptor wells of the Franz cells were maintainedat 37° C. (temperature on the surface of the skin is ˜31° C.) in astirring dry block with continual agitation via a stir bar. Samples weredrawn from the receptor wells at varying time points. Measurements weremade in six-fold replicates. The concentration of diclofenac in thesamples was analyzed using high performance liquid chromatography. Theinventive formulations performed better than the comparator at thelimits of finite dosing—finite dosing being a much better predictor ofthe performance of a formulation in an in vivo situation as opposed toinfinite dosing.

A) Gel Formulations Derived from a Comparative Liquid Base SolutionExample 2 Gel Formulations Using Various Thickeners in a ComparativeLiquid Formulation Base Solution

Initially, several thickeners including carbomers, polyvinylpyrrolidone, locust gum, cellulose polymers and polyvinyl alcohol weretested for their effectiveness at forming a diclofenac sodium gel usingthe comparative liquid formulation as a base solution. In the gelformulations of this Example, a comparative liquid formulation solutionwas produced and a thickener was then added directly to this base. Inorder to facilitate the incorporation of the thickener, sonication andheating (at 60° C.), along with vigorous vortexing/homogenization wereperformed.

Some thickeners, specifically guar gum, locust bean gum, methocel(HPMC), polyvinyl alcohol, and poloxamer 407 failed to form stable gels.In particular, immediate separation, inefficient thickening, andinsolubility of the thickeners was noted. Gels were formed that showedinitial stability with several cellulose polymers including hydroxyethylcellulose (Natrosol HHX) and hydroxypropylcellulose (HY119). Otherthickeners that showed an initially stable gel were PVP, and acrylicpolymer thickeners. The specifics of gel formulation for each thickenerare provided below:

HEC Thickening Agents:

A lower weight molecular weight hydroxyethyl cellulose (specificallyHydroxyethyl Cellulose (HEC) Type 250 M Pharm (Natrosol®)) was dispersedin the mixture of dimethyl sulfoxide, propylene glycol, glycerine andwater and allowed to swell for about 1 hour. Diclofenac sodium wasdissolved in ethanol and added to the HEC/solvent blend to obtain afinal formulation. Although HEC gels form relatively easily anddemonstrate a good flux profile, the gels are yellowish in color and aresusceptible to phase separation over extended periods of storage. Table2 shows the compositions of these formulations, and the resulting fluxvalues of these compositions as compared with a comparative liquidformulation are shown in FIG. 1.

PVP Thickening Agents:

PVP was added at up to 8% w/v after all other components of thecomparative liquid base formulation were mixed. PVP gels are clear innature, but suffer from an undesirable tacky feel when drying. Table 2and FIG. 1 shows the composition and flux data for this gel. In thisexample, Franz diffusion cells were dosed at 15 mg per Franz cell. Ascan be seen in FIG. 1, PVP gels performed reasonably well, but theirundesirable aesthetic qualities do not make them ideal for a commercialembodiment.

TABLE 2 Components of HEC and PVP gels used to generate the flux ratedata shown in FIG. 1. Formulation name Compar- Hec1b Hec2b PVP1b PP54ative Percentages in wt/wt % wt/wt % wt/wt % wt/wt % wt/wt % Water 18.8118.81 18.81 18.31 18.81 Dimethyl Sulfoxide 45.5 45.5 45.5 45.5 45.5Propylene glycol 11.2 11.2 11.2 11.2 11.2 Ethanol 11.79 11.79 11.7911.79 11.79 Glycerine 11.2 11.2 11.2 11.2 11.2 Diclofenac Sodium 1.5 1.51.5 2 1.5 Thickener HEC HEC PVP Carbopol none 971 w/vol % thickener 1.11.3 8 1 added to solution

Carbopol Thickening Agents:

Carbopol gels were formed by: (1) dispersing an acrylic polymer into amixture of water, glycerol, and propylene glycol followed by stirringfor 1 hour; (2) preparing a second solution of 1.5% diclofenac sodiumdissolved in ethanol and DMSO; (3) mixing the diclofenac solution intothe carbopol phase. An alternate method for forming carbopol gels is asfollows: (1) dispersing the carbopol into dimethyl sulfoxide andstirring for 1 hour; (2) dissolving diclofenac sodium in anethanol/water/propylene glycol mixture; (3) dispersing glycerol into thediclofenac solution; and (4) mixing the diclofenac solution into thepolymer/dimethyl sulfoxide blend, and stirring for 1 hour at ambienttemperature. These methods of mixing can be carried out at roomtemperature, or elevated temperature if desired. Varying carbopols wereused to make gels including: Carbopol 1342, 941, 971, 981, 974 andUltrez 10 (Noveon, Inc.). All carbopol gels were clear, proved stable toboth freeze-thaw cycling and incubation at elevated temperature (50° C.)for one month, and had good flow characteristics. Tables 2, 3, and 4show the composition of these gels, and FIGS. 1, 2, and 3 show theirrelative flux. A stable and clear gel could be formed at carbopolconcentrations of ˜>0.3% w/w when making gels with 1.5% w/w diclofenacsodium. For gels with 2% w/w diclofenac sodium, ˜>0.9% w/w carbopol wasneeded to make a stable gel. The exact amount of carbopol needed to froma gel depended on the type of carbopol used.

For the formulations of Table 3, Franz diffusion gels were dosed with200 μl per Franz cell. Carbopol gels uniformly showed increased fluxrates over the comparative formulation (see FIG. 2). Thicker gels (i.e.gels with higher weight percent carbopols) tended to have less flux thana composition with a lower weight percentage of the same carbopol.

TABLE 3 Components of gels made with Carbopol 981 and Ultrez 10 used togenerate the flux rate data shown in FIG. 2. Formulation name PUA PUBPUC P981a P981b P981c Comparative Percentages in wt/wt % wt/wt % wt/wt %wt/wt % wt/wt % wt/wt % wt/wt % Water 18.81 18.81 18.81 18.81 18.8118.81 18.81 Dimethyl Sulfoxide 45.5 45.5 45.5 45.5 45.5 45.5 45.5Propylene glycol 11.2 11.2 11.2 11.2 11.2 11.2 11.2 Ethanol 11.79 11.7911.79 11.79 11.79 11.79 11.79 Glycerine 11.2 11.2 11.2 11.2 11.2 11.211.2 Diclofenac Sodium 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Thickener UltrezUltrez Ultrez Carb 981 Carb 981 Carb 981 none w/vol % thickener 0.901.03 1.16 .90 1.06 1.22 added to solution

Antioxidants and chelating agents can also be added to the carbopol,HEC, or PVP gels. The addition of EDTA to carbopol gels by itself leadsto a slightly cloudy gel. BHA gels turned color with incubation athigher temperature. The mixture of BHT and EDTA to carbopol gels did notshow any discoloration and remained clear. For the formulations of Table4, Franz diffusion cells were dosed at 50 μl per cell. FIG. 3 shows fluxrates from these gels. Additions of chelating agents and preservativeshad no effect on flux rates.

TABLE 4 Components of gels made with carbopol 971 and carbopol 981 gelsused to generate the flux rate data shown in FIG. 3. Formulation nameCompar- PP51 PP52 PP53 ative 2% Percentages in wt/wt % wt/wt % wt/wt %wt/wt % Water qs qs qs 18.31 Dimethyl Sulfoxide 45.5 45.5 45.5 45.5Propylene glycol 11.2 11.2 11.2 11.2 Ethanol 11.79 11.79 11.8 11.79Glycerine 11.2 11.2 11.2 11.2 Diclofenac Sodium 2 2 2 2 BHT 0.1 0.1 EDTA0.05 0.05 Thickener Carbopol Carbopol Carbopol none 971 971 981 wt/wt %thickener 1 1 0.9

B. Comparative Examples Example 3 Comparison of Transdermal Flux ofVarious DMSO Gel Formulations Versus a Comparative Liquid Formulation

A series of diclofenac gel formulations were made wherein the basesolution was changed from the comparative base formulation. Inparticular, the weight percent of propylene glycol, ethanol, glycerine,water, and diclofenac were varied. In these new formulations, the weightpercent of the constituent chemicals was as follows: 45.5% DMSO, 20-30%ethanol, 10-12% propylene glycol, 0-4% glycerine, 2% diclofenac sodium,thickener and water added to 100% w/w.

Several thickeners were tested in this new base solution. A number ofthese thickeners failed to form stable gels; in particular, carbopolgels did not remain stable. However, cellulose gels were uniformlyeffective at forming gels. The most aesthetically pleasing of these gelswas formed with hydroxypropylcellulose (HY117, HY119, HY121). These gelsspread easily, were uniform in nature, dried quickly, and demonstratedgood flow characteristics.

Hydroxypropylcellulose gels were formed by mixing all the constituentparts and then adding the thickener at the end followed by agitation.The gel can also be formed by dispersing the hydroxypropylcellulose inthe aqueous phase prior to solvent addition. Heat can be used tofacilitate gel formation. Hydroxypropylcellulose gels were clear andflowed easily. They remain stable for at least six months demonstrating:no phase separation, negligible shift in pH, and low amounts ofdegradation products (<0.04%). The data in FIGS. 4-9, derived from theformulations of Tables 5-10, indicate that the hydroxypropylcellulosegel formulations of diclofenac sodium of the present invention alsoprovide a transdermal flux rate that is as much as 4-fold higher than acomparative liquid formulation.

Studies were performed to determine the relative transdermal flux ofvarious diclofenac gel formulations of the present invention whencompared with a comparative liquid formulation of U.S. Pat. Nos.4,575,515 and 4,652,557 (“Comparative” in Tables 5-10). Accordingly, theFranz cell procedure described above was used to compare diclofenac fluxrates of various diclofenac gel formulations with comparative liquidformulations.

For the formulations of Table 5, Franz cells were dosed at 10 mg perFranz cell. A new gel (F14/2) has an altered base solution over thecomparative liquid formulation and demonstrates both faster drying timesand better flux kinetics (see FIG. 4). The flux rates for these gels isnot as high as the carbopol gels (F971), but the drying rate issubstantially faster.

TABLE 5 Components of various gels and a comparative liquid formulationused to generate the flux rate data shown in FIG. 4. Formulation nameCompar- F14/2 F14/2 ative gel 2.5% gel 4.0% F971 Percentages in wt/wt %wt/wt % wt/wt % wt/wt % Water 18.81 12.5 12.5 17.16 Dimethyl Sulfoxide45.5 45.5 45.5 45.5 Propylene glycol 11.2 11 11 11.2 Ethanol 11.79 26.525 11.79 Glycerine 11.2 11.2 Diclofenac Sodium 1.5 2 2 2 Thickener noneHY119 HY119 Carbopol 971 wt/wt % thickener 2.5 4 1.15

For the formulations of Table 6, Franz diffusion cells were dosed at 7mg per cell. Lowering the pH shows a marked increase in flux rates (seeFIG. 5).

TABLE 6 Components of various gels and a comparative liquid formulationused to generate the flux rate data shown in FIG. 5. Formulation nameComparative F14/2 gel 2.5% F14/2 gel 4.0% F971 F14/2 gel 2.5% + HCLPercentages in wt/wt % wt/wt % wt/wt % wt/wt % wt/wt % Water 18.81 12.512.5 17.16 12.5 Dimethyl Sulfoxide 45.5 45.5 45.5 45.5 45.5 Propyleneglycol 11.2 11 11 11.2 11 Ethanol 11.79 26.5 25 11.79 26.5 Glycerine11.2 11.2 Diclofenac Sodium 1.5 2 2 2 2 concentrated HCL *** added to pH5.3 pH 9 9.43 9.67 6.77 5.3 Thickener none HY119 HY119 Carb971 HY119wt/wt % thickener 2.5 4 1.15 2.5

For the formulations of Table 7, Franz cells were dosed at 7 mg perFranz cell. The resulting flux rates for each of these formulations isshown in FIG. 6.

TABLE 7 Components of various gels used to generate the flux rate datashown in FIG. 6. Formulation name Comparative F14/2 gel 2.5% HaCa2 HaCaF14/2 gel pH 5.3 Percentages in wt/wt % wt/wt % wt/wt % wt/wt % wt/wt %Water 18.81 12.5 22.3 26.3 12.5 Dimethyl Sulfoxide 45.5 45.5 45.5 45.545.5 Propylene glycol 11.2 11 11.2 11.2 11 Ethanol 11.79 26.5 12 12 26.5Glycerine 11.2 6 2 Diclofenac Sodium 1.5 2 2 2 2 concentrated HCL ***added to pH 5.3 pH 9 9.43 6.8 6.71 5.3 Thickener none HY119 Carbopol 971Carbopol 971 HY119 wt/wt % thickener 2.5 1 1 2.5

For the formulations of Table 8, the comparative liquid formulation(1.5% diclofenac sodium) was dosed at 20 mg per Franz cell. Solaraze® (acommercially available 3% diclofenac sodium gel) was dosed at 10 mg perFranz cell, and F14/2 was dosed at 15 mg per Franz diffusion cell. Atthis dosing, all cells were dosed with equivalent amounts of diclofenacsodium. F14/2 continued to show increased performance over otherformulations (see FIG. 7).

TABLE 8 Components of various diclofenac formulations used to generatethe flux rate data shown in FIG. 7. Formulation name ComparativeSolaraze ® F14/2 gel 2.5% Percentages in wt/wt % wt/wt % wt/wt % Water18.81 12.5 Dimethyl Sulfoxide 45.5 45.5 Propylene glycol 11.2 11 Ethanol11.79 26.5 Glycerine 11.2 Diclofenac Sodium 1.5 3 2 Thickener none HY119wt/wt % thickener 2.5

For the formulations of Table 9, the comparative liquid formulation wasdosed at 0.9 mg per Franz cell at 0, 4, 8, and 12 hrs. F14/2 was dosedat 1.5 mg per Franz cell at 0 and 6 hrs. The accumulated dose from thegel was considerably higher in comparison to the comparative solution,providing a ˜1.5 fold increase in flux (see FIG. 8).

TABLE 9 Components of formulations used in the multidosing experimentsof FIG. 8. Formulation name Comparative F14/2 gel 2.5% F14/2 gel pH 8.5Percentages in wt/wt % wt/wt % wt/wt % Water 18.81 12.5 45.5 DimethylSulfoxide 45.5 45.5 11 Propyelene glycol 11.2 11 26.5 Ethanol 11.79 26.512.5 Glycerine 11.2 Diclofenac Sodium 1.5 2 2 concentrated HCL *** addedto pH 8.5 Thickener none HY119 HY119 wt % thickener 2.5 4\2.5

For the formulations of Table 10, Franz cells were dosed at 20 mg percell. The resulting flux rates for these formulations is shown in FIG.9.

TABLE 10 Flux results from varying diclofenac formulations. Franz cellswere dosed at 20 mg per cell. Formulation name F14/2 F14/2 Compar-Compar- gel 3.5% solution F971 ative 2% ative Percentages in wt/wt %wt/wt % wt/wt % wt/wt % wt/wt % Water 12.5 12.5 17.16 18.31 18.81Dimethyl 45.5 45.5 45.5 45.5 45.5 Sulfoxide Propylene 11 11 11.2 11.211.2 glycol Ethanol 25.5 29 11.79 11.79 11.79 Glycerine 11.2 11.2 11.2Diclofenac 2 2 2 2 1.5 Sodium Thickener HY119 none Carb 971 none nonewt/wt % 3.5 1.1 thickener

Example 4 Comparative Data on Transdermal Flux of Various DiclofenacGels

Studies were performed to determine the relative transdermal flux of thediclofenac gel formulations of the present invention when compared withpreviously disclosed formulations, such as the diclofenac diethylaminegel formulation described by Baboota (Baboota et al., Methods Find. Exp.Clin. Pharmacol., 28: 109-114 (2006)). Accordingly, the Franz cellprocedure described above was used to compare flux rates of three of thediclofenac formulations described by Baboota with a gel vehicle of thepresent invention. The diethylamine form of diclofenac was used as theactive agent, as that is the form used by Baboota. The exactcompositions of the formulations used in this study are shown in Table11 below. The Baboota formulations are labeled FY1, FY2, and FY3, whilea gel formulation using the vehicle of the present invention withdiclofenac diethylamine as the active is labeled G14/2_m. A comparativeliquid formulation was also included in this study (“Comparative”).Among the primary differences between the composition of Baboota'sformulation and that disclosed in the present invention is the higherDMSO concentrations in the present formulations (45.5% w/w versus 10%w/w).

As is apparent from the data shown in FIG. 10, although the Babootaformulation is also a gel, the vehicle of the present invention providesa significantly greater flux rate. After 12 hours, the gel of thepresent invention provides an accumulated dose of 26.8 μg/cm² versus 8.9μg/cm² for Baboota's best performing gel. Thus, the gel of the presentinvention has a nearly 3-fold greater rate of flux and accumulation ofdiclofenac than a similar gel, as described by Baboota. Note that theseexperiments were conducted at finite dosing which is more representativeof clinical dosing of a non-occluded composition that is appliedperiodically but which is not meant to be in continuous contact with theskin. Additionally, the Baboota gels also contained a higher percentageof the active agent, 3.4% w/w as compared to 2% w/w for the compositionsusing the vehicle of the invention.

Other advantages were also observed, including the consistency andstability of the gel of the present invention when compared with theBaboota gel. In contrast to the smooth and uniform consistency of thepresent gel, the Baboota gel formulations were cloudy and lumpy, thus,unable to maintain a gel-like consistency. For this reason, the Babootacompositions would be expected to have some stability issues and a shortshelf life.

Thus, despite both being gel formulations, when a head-to-headcomparison is performed, using a finite dosing protocol, the formulationof the present invention is significantly more effective at thetransdermal delivery of a diclofenac active agent, when compared withanother gel formulation, that described by Baboota et al. Furthermore,as shown in FIG. 7, the formulation of the present invention alsoperformed remarkably better when compared to a diclofenac gel,Solaraze®, a product currently sold on the market. Thus, the presentinvention provides a diclofenac sodium gel formulation that hasunexpectedly superior properties (e.g., with respect to parameters suchas transdermal flux rates, favorable composition consistency, andgreater stability and self life) when compared to the previouslydisclosed diclofenac diethylamine gel formulation described by Babootaor the diclofenac sodium formulation embodied by the Solaraze® gel.

TABLE 11 Components of diclofenac diethylamine gels used to generate theflux rate data shown in FIG. 10. For the formulations of Table 11, Franzdiffusion cells were finite dosed at 4 mg per cell. Formulation nameCompar- FY1 FY2 FY3 G14/2_m ative_m Percentages in wt/wt % wt/wt % wt/wt% wt/wt % wt/wt % Dimethyl 10 10 10 45.5 45.5 Sulfoxide Ethanol 25 25 2526.5 11.79 PEG 400 15 15 15 Propylene 15 15 15 11 11.2 glycoltriethanolamine 0.5 0.5 0.5 DMSO Water qs qs qs 12.5 18.81 Sodium 6carboxymehtyl- cellulose Glycerine 11.2 Thickener Carb 940 PVA Carb 940HY119 none wt % 1 20 0.5 2.5 Thickener Active: 3.4 3.4 3.4 2 1.5diclofenac diethylamine wt %

Example 5 Comparison of Drying Time/Residual Weight of a ComparativeLiquid Formulation Solution Versus the Corresponding Gel

In order to evaluate the drying time of a comparative liquid formulationsolution as compared to the corresponding gel, the study described inthis example was performed. Equal weight amounts (100 mg) of either thecomparative liquid formulation solution or diclofenac sodium gelformulations were measured on to plastic weigh dishes and spread over a10 cm² area, and then left exposed to ambient conditions. At selectedtime points, the plastic weighing dishes were again weighed to determinethe mass of the composition remaining on the weighing dish. As shown bythe data in Table 12 below and in FIG. 11, it was surprisingly foundthat even after a 24 hour drying period, almost all (nearly 90%) of theweight of the initially applied comparative liquid formulationcomposition remained on the weighing dish. Thus, the weight of thecomparative liquid formulation changed very little over the time pointsmeasured, indicating that the drying of the liquid formulation occurredvery slowly.

In contrast, even within the first five minutes, the three gelformulations displayed more rapid drying than the liquid formulation.70% of the weight of the two gels that contained 2% or 4% HPC remained,as compared to the over 90% of the liquid formulation which remained,after 4 hours of drying time. By 24 hours, this difference was even morepronounced, as slightly over 20% and 30% of the weight of the two gelformulations containing 2% and 4% HPC, respectively, remained, andslightly under 60% of the weight of the F971 gel remained, as comparedto the almost 90% of the liquid formulation which remained. This is asurprising result, as one would have expected the liquid formulation tolose weight more quickly, and thus have a shorter drying time, ascompared to a semi-solid gel formulation. Thus, this exampledemonstrates that the gel compositions of the present invention displaysuperior drying characteristics as compared to a comparable liquidformulation.

Thus, in certain embodiments, the present invention provides aformulation which has a drying time such that, at most, a 50% weight ofthe starting amount remains as a residue after 24 hours of drying time,preferably a 30-40% or less weight of the starting amount remains as aresidue after 24 hours of drying time.

The improved drying time of the gel formulations of the presentinvention provides improved ease of use and is expected to lead tobetter patient compliance. Thus, this invention provides a gelformulation with improved drying characteristics while also providingimproved drug delivery, as evidenced by the advantageous transdermalflux data shown in the examples above.

TABLE 12 Drying times for gels and a comparative liquid formulationsolution. Equal weights of each formulation were measured and spread onweigh dishes. The weight of each remaining formulation was then followedwith time. The gels of this invention showed faster drying kinetics thanthe comparative liquid formulation, with F14/2 showing the fastestdrying rate. These gels also had improved “spreadability”characteristics, which most likely contributed to this improvement indrying rates. Drying times Formulation name Compar- F14/2 F14/2 ativegel 2.5% gel 4.0% F971 Percentages in wt/wt % wt/wt % wt/wt % wt/wt %Water 18.81 12.5 12.5 17.16 Dimethyl 45.5 45.5 45.5 45.5 SulfoxidePropyelene 11.2 11 11 11.2 glycol Ethanol 11.79 26.5 25 11.79 Glycerine11.2 11.2 Diclofenac 1.5 2 2 2 Sodium Thickener none HY119 HY119Carbopol 971 wt/wt % 3.5 2.5 4 1.15 thickener % Remaining Compar- F14/2F14/2 Time (hr) ative gel 2.5% gel 4.0% F971 0.000 100 100 100 100 0.08398.1 93 92.6 100.3 0.167 96.7 92.9 91.8 100.3 0.333 95.7 92.7 93 100.20.500 95.6 92.7 93.3 100 0.750 95.5 92.1 92.3 99.8 1.000 95.9 92 91.899.7 4.000 93 71 70.7 86.8 24.000 88.7 32.4 23.5 58.8

Example 6 Comparison of Stability Characteristics of a ComparativeLiquid Formulation Versus Diclofenac Sodium Gel Formulations

This example provides a comparison of the stability of the compositionsof the present invention tested against reference formulations at roomtemperature over a six month period. It was unexpectedly found thatwhile the compositions of the invention contain a higher concentrationof active agent, they in fact resulted in a lower concentration of adegradation impurity as compared to the reference. It was alsounexpectedly found that compositions using hydroxypropylcellulose (HPC)as the gelling agent had a significantly lower quantity of this impurityas compared to compositions made using carbomer gelling agents.

In this study, samples of the test compositions were placed into plasticscrew cap bottles which were sealed and held at 25° C. at 60% humidityfor 6 months. After the 6 month storage period, the samples were testedfor impurities by high performance liquid chromatography (HPLC). Theactive agent, diclofenac sodium, was found to elute by HPLC with anelution time of about 11 minutes. It was found that upon 6 months ofstorage, an impurity, termed “impurity A”, was seen to elute at about6.6 minutes in varying amounts for the various compositions as shown inTable 13 below.

TABLE 13 Percent “impurity A” after Composition 6 months of storage(wt/wt) 1.5% diclofenac sodium as a comparative 0.034% liquidformulation solution 2.0% diclofenac sodium in 0.9% Carbopol 0.09% gel2.0% diclofenac sodium in 3.5% HPC gel 0.02%

Thus, as indicated by the data in Table 13, while having a higherconcentration of the active agent, diclofenac sodium, a gel formulationof the present invention containing 3.5% HPC shows a higher degree ofstability, as reflected in the appearance of a lower percentage of“impurity A” as compared to a comparable liquid formation. The datashown in Table 13 also shows that the HPC gel formation is more stablethan a comparable gel formation containing 0.9% Carbopol, as the HPC gelformation demonstrates an at least 4-fold reduction in the level ofimpurity A. Thus, a gel formation of the present invention providesimproved stability of the active agent as compared to the referenceformulations as evidenced in a formulation which degrades by less than0.034% or 0.09%, over 6 months, as was observed for the referenceformulations. Furthermore, the amount of “impurity A” found in the gelformulation of the present invention after a 6 month storage periodwould result in an exposure level well below limits that would requireadditional nonclinical testing testing of the impurity.

Example 7 Comparison of In Vivo Epicutaneous Absorption of Liquid VersusGel Formulations

A study was conducted to compare systemic absorption after topicalapplication (also referred to as epicutaneous absorption) of acomparative solution with a gel of the invention. A parallel design wasemployed with 6 Landrace pigs per arm. Drug was applied for 7 days withan additional dose on Day 8. Blood was sampled on Day 1 to determine abaseline; Day 6, Day 7 and Day 8 samples were taken to confirm steadystate, and additional samples were taken at 0 hr, 2 hr, 5 hr, 7 hr, 12hr, 15 hr, and 24 hr on Day 7 to determine a 24 hour steady stateprofile; samples taken from Days 8-13 were used to determine anelimination profile.

The doses used in this study were as follows: The comparative solutiongroup received 3.85 mg diclofenac sodium per administration and animal 4times daily; the gel Group received 8.08 mg diclofenac sodium peradministration and animal 2 times daily; the administration area was 5cm×10 cm/animal. These amounts represent the scaled human clinicaldoses.

Sufficient blood was collected from each animal per sampling time andprocessed for at least 2 mL Li-Heparin plasma/sample, which were splitinto two aliquots of 1 mL each. Blood was withdrawn from all animals asshown in Table 14.

TABLE 14 Blood sampling schedule Test No. of No. of Day(s) Samplingtimes samples aliquots 1 0 (prior to first administration) 24 48 6 0(prior to first administration), 24 48 7 0 (prior to firstadministration), 168 336 2 hr post first dosing, 5 hr post first dosing(prior to second administration for Group 1), 7 hr post first dosing, 10hr post first dosing (prior to third administration for Group 1 andprior to second administration for Groups 2, 3, and 4.) 12 hr post firstdosing 15 hr post first dosing (prior to fourth administration forGroup 1) 8-13 0 (pre-dose), 4, 8, 12, 24, 48, 72, 96, 216 432 and 120 hrpost administration Total number 432 864 of samples

Pharmacokinetic evaluation of the plasma data was performed using TopFit2.11. A non-compartment model was used for the calculation of theterminal half life and area under the curve (AUC). Elimination rateconstants (K_(el)) and plasma elimination half-lives (t_(1/2)) werecalculated by linear regression analysis of the log/linear portion ofthe individual plasma concentration-time curves (c=concentration,t=time). Half-life was determined using the formulae:t _(1/2)=ln 2/K _(el) [h]dc/dt=(K _(el))(c)[h].

Area under the curve (AUC) values were calculated using the lineartrapezoidal method and extrapolated to infinite time by dividing thelast measurable plasma concentration by the terminal elimination rateconstant. Plasma concentrations at time zero were taken to be those atthe pre-dose blood sampling time on Test Day 8. Area under the curve(AUC) was calculated using the formula:AUC=[∫c dt](ng/mL)(h), integrated from zero to infinity.

The following pharmacokinetic parameters for diclofenac sodium werecalculated:

AUC₀₋₂₄ (Test Day 7)

AUC_(0-t) (Test Day 8)

AUC_(0-inf) (Test Day 8)

T_(max) (Test Days 7, 8) (time to reach C_(max))

C_(max) (Test Days 7, 8) (maximum observed plasma concentration)

C_(min) (Test Days 7, 8) (minimal observed plasma concentration)

C_((trough)) (Test Days 6, 7, and 8) (trough plasma concentration)

K_(el) (elimination half-life)

T_(1/2) (plasma elimination half-life).

The achievement of steady state was assessed by using repeated measuresANOVA with log-transformed trough concentrations on Test Days 6, 7, and8 as the dependent variable, time as the independent variable, subjectas a random effect, and day as a fixed effect.

The data is shown in FIG. 12 and Tables 16 and 17. Compositions of theinvention show significantly more absorption of diclofenac sodium asmeasured by the mean AUC. This result holds even when adjusting fordose.

TABLE 15 Dosing in pigs Diclofenac Area of Dose of the Diclofenac NumberDiclofenac Sodium application product per Sodium of doses per day %(w/w) (cm²) application (mL) per dose (mg) per day (mg) Gel 2.0 50 0.408.08 bid 16.2 Comparative 1.5 50 0.24 3.85 qid 15.4 Solution

TABLE 16 PK profile at steady state on Day 7 Tmax Cmax AUC 0-24treatment subject (h) (pg/ml) (pg*h/ml) Gel 13 12 15379 239818 14 108570 175862 15 5 6014 104122 16 5 4827 63842 17 15 434829 2689765 18 2414484 231494 Mean 12 80684 584151 SD 7 173549 1033866 Comparative 1 108302 107122 Solution 2 10 24709 133521 3 15 14743 160294 4 0 4350 442675 24 9552 112460 6 12 8628 77881 Mean 12 11714 105924 SD 8 7185 40865

TABLE 17 Relative bioavailability and exposure to a comparative liquidformulation in comparison to the corresponding gel at steady state RatioGel/Comparative Solution % C_(max) 167.7 C_(max)/Dose 161.5 AUC 0-24241.1 AUC 0-24/Dose 232.2

Example 8 Clinical Trials of Diclofenac Gel in the Treatment ofOsteoarthritis

A clinical trial will be performed to evaluate the safety and efficacyof a gel formulation of the present invention in subjects with symptomsof primary osteoarthritis (OA) of the knee. Specifically, a 2-arm,double-blinded, placebo-controlled, randomized, 12-week Phase IIIclinical trial will be performed in 300 subjects randomized to receiveeither a diclofenac gel formulation, placebo gel (the gel carriercontaining no diclofenac). Subjects will apply 2 mL of study gel totheir OA knee per application.

The primary variables for assessment of efficacy will be the WOMAC LK3.1pain and physical function and Patient Overall Health Assessment.Secondary variables will be the WOMAC stiffness and Patient GlobalAssessment. The primary efficacy analyses will be the comparison of thechange from baseline to final assessment of the primary efficacyvariables for subjects in the diclofenac sodium gel arm versus theplacebo gel arm.

More specifically, the efficacy of diclofenac gel on knee OA symptomswill be measured by the subjective response of subjects as determined byan efficacy variables questionnaire which includes the WOMAC LK3.1 OAIndex (pain, physical function, and stiffness dimensions), a PatientOverall Health Assessment, and a Patient Global Assessment. (SeeBellamy, N., WOMAC Osteoarthritis Index User's Guide IV, Queensland,Australia (2003)).

The WOMAC LK3.1, Patient Overall Health Assessment and Patient GlobalAssessment questionnaires will be based on the five-point Likert scale.Numerical values will be assigned to WOMAC LK3.1 scores, Patient GlobalAssessment scores and Patient Overall Health Assessment scores, asfollows:

Patient Overall Health Assessment and WOMAC LK3.1 Patient GlobalAssessment

None=0 Very Good=0

Mild=1 Good=1

Moderate=2 Fair=2

Severe=3 Poor=3

Extreme=4 Very Poor=4.

The WOMAC LK3.1 OA Index is a segregated, multidimensional,self-administered index with three independent dimensions: pain,stiffness and physical function and will be used as an efficacy variablein this study.

In a preferred embodiment of the invention, application of the gelformulations of the invention when applied topically will result in areduction of pain or physical function on the WOMAC scale of at least 1Likert scale unit over a 12 week period. Even more preferably, areduction of 2, 3, or 4 Likert scale units will result. Most preferably,application of the gel formulations of the invention will result incomplete relief of pain and complete or nearly complete restoration ofphysical function.

To assess safety, the frequency of adverse effects will be tabulated,the worst skin irritation score will be documented, and change in vitalsigns and laboratory parameters will be assessed.

The foregoing discussion of the invention has been presented forpurposes of illustration and description. The foregoing is not intendedto limit the invention to the form or forms disclosed herein. Althoughthe description of the invention has included description of one or moreembodiments and certain variations and modifications, other variationsand modifications are within the scope of the invention, e.g., as may bewithin the skill and knowledge of those in the art, after understandingthe present disclosure. It is intended to obtain rights which includealternative embodiments to the extent permitted, including alternate,interchangeable, and/or equivalent structures, functions, ranges, orsteps to those claimed, whether or not such alternate, interchangeable,and/or equivalent structures, functions, ranges, or steps are disclosedherein, and without intending to publicly dedicate any patentablesubject matter.

All publications, patents and patent applications referred to herein areincorporated by reference in their entirety to the same extent as ifeach individual publication, patent or patent application wasspecifically and individually indicated to be incorporated by referencein its entirety.

What is claimed is:
 1. A method for treating pain, said methodcomprising: administering a formulation to a patient in need thereof,wherein the formulation comprises: 2% w/w of diclofenac sodium; 30-60%w/w of DMSO; 1-15% w/w of propylene glycol; 1-30% w/w of ethanol; water;a viscosity of 500-5000 centipoise; and at least one thickening agentselected from the group consisting of a cellulose polymer, a carbomerpolymer, a carbomer derivative, a cellulose derivative, and mixturesthereof, wherein the administration of the formulation is twice daily,to thereby effectively treat pain.
 2. The method of claim 1, wherein theconcentration of DMSO is about 40% to about 50% w/w.
 3. The method ofclaim 2, wherein the concentration of DMSO is a member selected from thegroup consisting of 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% and50% w/w, and all fractions in between.
 4. The method of claim 1, whereinthe concentration of ethanol is present at 23-29% w/w.
 5. The method ofclaim 1, wherein the at least one thickening agent is selected from thegroup consisting of a carbomer polymer, a carbomer derivative andmixtures thereof.
 6. The method of claim 5, wherein the at least onethickening agent is selected from the group consisting of carbopol 971,carbopol 981, carbopol 941, carbopol 1342 and ultrez
 10. 7. The methodof claim 6, wherein glycerine is present.
 8. The method of claim 1,wherein the at least one thickening agent is selected from the groupconsisting of a cellulose polymer, a cellulose derivative, and mixturesthereof.
 9. The method of claim 8, wherein the at least one thickeningagent is hydroxypropyl cellulose.
 10. The method of claim 1, wherein theformulation comprises: 40-50% w/w of DMSO; 23-29% w/w of ethanol; and10-12% w/w of propylene glycol.
 11. The method of claim 10, wherein theconcentration of DMSO is a member selected from the group consisting of40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% and 50% w/w, and allfractions in between.
 12. The method of claim 1, wherein the formulationhas improved absorption on a per dose basis compared to a comparativeliquid composition.
 13. The method of claim 1, wherein the pain is dueto osteoarthritis.